Temporospatial localization pattern of PRRX1 and PRRX2 suggests essential roles in differentiation into hormone-producing cell and vascular cells during rat pituitary organogenesis

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 112-141-Hypothalamus-Pituitary Development & Biology
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-122
Masashi Higuchi*, Saishu Yoshida, Mitsuyoshi Tsuda, Shiori Shibuya, Hiroki Ueharu, Masayo Sekita, Hideji Yako, Naoko Kanno, Mo Chen, Takako Kato and Yukio Kato
Meiji University, Kawasaki, Kanagawa, Japan
Paired-related homeobox transcription factors, Prrx1 and Prrx2, have been verified to play essential roles in limb, heart, and craniofacial development. However, in situ hybridization studies on the expression pattern of Prrx1 and Prrx2 so far provided insufficient data for a pituitary. Recently, we demonstrated the existence of PRRXs-positive cells using antibody against PRRX2, which is cross-reactive with PRRX1 and PRRX2, and confirmed Prrx1 and Prrx2 mRNAs in the rat embryonic pituitary. Furthermore, double immunostaining with SOX2, a stem/progenitor marker, revealed that PRRXs-positive (PRRXs+) cells are composing of two populations, SOX2-positive (PRRXs+/SOX2+) and -negative (PRRXs+/SOX2-), in the embryonic pituitary. However, most of these studies could not provide confirmative information for PRRX1 and PRRX2. At least two issues are remained to be clarified; one is the roles of the two cell types found in PRRXs+cells and the second is whether PRRX1 and PRRX2 coexist or not.

In this study, we started to generate specific antibodies that are able to recognize each PRRX1 and PRRX2, and succeeded in production of the antibodies specific for each. We first analyzed temporospatial localization of PRRX1 and PRRX2 by immunohistochemistry using novel specific antibodies as well as SOX2 and some vascular markers, such as isolectin B4. The results indicated that PRRX1+ cells were present in the anterior and intermediate lobes, especially on the marginal cell layer postulated as a stem cell niche from late embryonic stage to early postnatal stage. PRRX1 co-localized with SOX2 in the marginal cell layer of the anterior and intermediate lobes, and was observed in a few hormone-positive cells in the parenchyma of the anterior lobe. In contrast, PRRX2+ cells were not detected at embryonic stage but were definitely observed within some of SOX2+ cells lining the marginal cell layer at postnatal stage. In addition, each PRRX1+ and PRRX2+cell was present in the surrounding mesenchyme and invaded the embryonic pituitary, followed by differentiation into vascular endothelial and smooth muscle cells.

In conclusion, analyses of the temporospatial localization pattern of PRRX1 and PRRX2 in rat pituitary development successfully demonstrated that PRRX1 and PRRX2 are present in the undifferentiated and transient differentiated hormone-producing cells and also in the surrounding mesenchymal cells, followed by differentiation into hormone-producing cells and vascular cells.

Nothing to Disclose: MH, SY, MT, SS, HU, MS, HY, NK, MC, TK, YK

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